Polyoxyalkylene bis-thiourea extreme pressure agents and methods of use

ABSTRACT

NOVEL SUBSTITUTED AND UNSUBSTITUTED POLYOXYALKYLENE BIS-THIOUREAS HAVING THE FORMULA: R-NH-C(=S)-NH-CH(-Y)-CH2-(O-CH2-CH(-Y))X-NH-C(=S)-NH-R WHEREIN X IS A NUMBER FROM 1 TO 10, R AND R1 ARE SELECTED FROM THE GROUP CONSISTING OF HYDROGEN, ALKYL AND ALKENYL, Y IS HYDROGEN OR LOWER ALKYL, ARE USEFUL AS EXTREME PRESSURE LUBRICANTS IN METAL WORKING FLUIDS AND PARTICULARLY IN AQUEOUS TYPE FLUIDS. COMPOSITIONS COMPRISING THE THIOUREAS AND A BOUNDARY LUBRICANT PROVIDE THE ANTI-WELD AND FRICTION REDUCTION PROPERTIES NECESSARY FOR HEAVY DUTY MACHINING.

United States Patent ()1 ice 3,798,164 Patented Mar. 19, 1974POLYOXYALKYLENE BIS-THIOUREA EXTREME PRESSURE AGENTS AND METHODS OF USEThomas J. Kmet, Midlothian, and Jon A. Loboda, Chicago, Ill., assignorsto The Richardson Company, Melrose Park, 1]].

No Drawing. Original application May 24, 1971, Ser. No. 146,535, nowPatent No. 3,704,321. Divided and this application Sept. 14, 1972, Ser.No. 289,203

Int. Cl. Cm 1/06, 1/38 U.S. Cl. 252-475 6 Claims ABSTRACT OF THEDISCLOSURE Novel substituted and unsubstituted polyoxyalkylenebis-thioureas having the formula:

BACKGROUND OF THE INVENTION This invention relates to a series of newand useful bisthiourea compounds including compositions and methods ofusing the same in machining operations. More specifically, it has beendiscovered that certain novel polyoxyalkylene bis-thioureas and theircompositions perform as extreme pressure agents when incorporated intometal working fluids. The invention is founded on the realization thatsuperior extreme pressure lubrication can be expected in heavy dutymachining operations particularly with aqueous base cutting fluids whenused in conjunction with the thioureas defined herein below. The instantthioureas are significant in that there are few sulfur containingextreme pressure agents available which can be effectively employed in awide range of aqueous systems. Thus, the instant compounds permit waterbased metal working solutions and emulsions to be used in a broaderrange of machining applications including heavy duty grinding andcutting operations.

Briefly, it has been discovered that a series of thioureas having theformula:

wherein x is a number from 1 to 10 and R and R are selected from thegroup consisting of hydrogen, alkyl and alkenyl and Y is hydrogen orlower alkyl, perform as extreme pressure (EP) agents in metal workingfluids and particularly those containing water.

Along with the extreme pressure agents shown herein, it is oftendesirable though not required in each instance to also employ boundarylubricants. Boundary lubrication is ordinarily used in machiningoperations to prevent heat build-up and unwanted wear which liquids suchas water, hydrocarbon oils, silicones etc. are unable to controlespecially as conditions become more extreme. However, it has been foundthat polar type boundary lubricants perform particularly well with theabove mentioned thioureas. It is believed that these lubricants act withthe extreme pressure agents to more effectively release sulfur from thethioureas to form protective iron sulfide films on the surface of theworkpiece when subjected to conditions of high pressure and temperature.Therefore, in addition to novel polyoxyalkylene bis thioureas, thepresent invention also contemplates compositions of said thioureasadvantageously used with boundary lubricants sometimes referred to aslubricity agents to enhance the activity of the extreme pressurecomponent.

As previously indicated, the EP additives of the present inventionprovide the necessary friction modification and wear reduction as wellas galling and seizing reducing properties making them highy versatileand satisfactory extreme pressure lubricants, especially useful inaqueous metal working fluids. Heretofore, compositions used inheavy-duty machining operations were mostly limited to non-aqueous oroil-based fluids. Aqueous metal working fluids, on the other hand,ordinarily in the form of solution or emulsion comprised of water ordiluted with water prior to use and perhaps containing in addition aboundary lubricant additive such as fatty acid soaps includingsulfoesters, alkyl taurines, alkylpolyamines, polyethylene glycols,petroleum sulfonate, sulfoaminoacetates, have been limited to machiningoperations where only relatively light or mild pressure between the workand cutting tool would be employed.

Generally, Water based metal working fluids used under light pressureprovide suflicient lubrication to prevent metal-to-metal contact.However, as pressures and temperatures rise between work and tool tomore extreme conditions, water-based compositions are unable to supplysufficient friction reduction or boundary lubrication. Frequently,pressure between the sliding chip and tool face is in the order of100,000 p.s.i. with temperatures in the area of contact at 1000 F. ormore. Under these conditions, aqueous films with boundary lubricantscommonly break down, greatly diminishing tool life and quality of finishon the work.

Sulfur containing metal working lubricants and extreme pressure agentssuch as sulfurized mineral and fatty oils, sulfochlorinated oils and thelike, have been used with some success. However, such products have notbeen entirely satisfactory in many instances. Frequently, extremepressure soluble oils made with conventional sulfurized fatty additiveshave been undependable because of their instability. Blends ofconventional sulfur containing extreme pressure additives and mineraloils either will not emulsify or will form inferior emulsions that breakwhen stored or used. Then too, the more stable sulfurized products wouldnot perform well because they did not release their sulfur underconditions of high temperature and pressure to provide essential EPlubrication.

Accordingly, it is a principal object of this invention to provide aseries of novel polyoxyalkylene bis-thiourea extreme pressure agents andprocess for their manufacture.

Another principal object is to provide metal-working compositionscomprising the bis-thiourea EP agents which possess good stability andshelf-life, but nevertheless release their sulfur to form protectivefilms under conditions of high temperature and pressure.

Another object is to provide complete aqueous base metal workingcompositions for use under extreme conditions during heavy dutymachining operations.

A still further object of the present invention is to provide a methodof machining under conditions of extreme pressure and temperature withpolyoxyalkylene bis-thiourea EP agents.

These and other objects, features and advantages of this invention willbecome apparent to those skilled in the art after a reading of thefollowing more detailed description.

SUMMARY OF THE INVENTION As stated above, this invention relates tonovel and useful thioureas. In particular, it is concerned withthioureas having their terminal nitrogens substituted and unsubstitutedwhich can be represented by the following formula:

wherein x, R, R and Y are as defined above. Their molecular weights aregenerally under 1000 and in most instances will range fromabout 250 to950. Each of the Rs may be hydrogen, but are preferably substituted withalkyl or alkenyl. When alkyl or alkenyl, they are advantageously 1 to 8carbon atoms, which includes lower alkyl radicals of l to 3 or 4 carbonatoms such as methyl, ethyl and propyl as well as lower alkenyls likeethylene, propenyl and allyl. These groups also include higher alkylsand alkenyls usually up to 8 carbon atoms, however, lower members arepreferred for better water solubility. The above formula contemplates inaddition to normal aliphatic radicals their usual isomeric forms such asiso-propyl, butyl, secondary and tertiary butyl and the like. Y may behydrogen, however, here too in most instances it will be lower alkyl ofl to 3 carbon atoms like methyl, ethyl and propyl.

In the above formula, x is a number from 1 to 10 with an intermediatepreferred range from about 3 to 6. Thioureas in which x is about 3 and5.6 have been specially advantageous.

Specific examples of a few of the thioureas contemplated within theinstant invention are represented in the following table.

Generally, the process for their preparation involves reacting apolyether diamine with an isothiocyanate. The reaction mixture is heatedfor several hours forming a homogeneous solution. The mixture is thentreated to remove the solvent used to dissolve the reactants.

Broadly, the polyether diamine reactant of this invention is apolyoxyalkylene diamine. It encompasses both linear and branched membershaving at least one and preferably a plurality of ether linkages andcontaining two terminal primary amino groups. Their molecular weightsgenerally range from about 100 to 700. These polyethers aresubstantially free from functional groups other than amino. They mayhave the following formula:

rated-by-reference herein. Polyethers of the kind described above areavailable under the trademark Jeffamine by Jefferson Chemical.

Alternatively, similar other amines of the following structure can beused:

f \CI-h/a O CH3 0/x \CHz/3 NHz wherein Y is hydrogen or lower alkyl of 1to 3 carbon atoms and x is a number from 1 to 10. A preferredillustrative example of such glycol diamines is di-(3-aminopropyl) etherof dipropylene glycol having the formula:

A These polyether diamines and process for their manufacture are taughtin U.S. Pat. 3,316,185 which disclosure is incorporated-by-referenceherein.

Isothiocyanates are reacted with the polyether diamines to form theadduct. Those isothiocyanates for use in the propyl) ether ofdipropylene glycol having the formula:

wherein Z is hydrogen, alkyl or alkenyl. When Z is alkyl or alkenyl,they are radicals of 1 to 8 carbon atoms corresponding with theaforementioned R substituents. Illustrative examples of specificisothiocyanates are isothiocyanic acid and their corresponding esterssuch as methyl, ethyl, propyl, allyl, isopropyl and the like.

Before charging the reaction vessel, the reactants are separatelydissolved in virtually any appropriate organic solvent such as benzene,acetone, toluene, xylene, various ethers like diethyl, methyl ethylethers as well as various alcohols such as methyl, ethyl, isopropyl,etc. The polyether amine reactant is preferably cooled below ambienttemperature to compensate for the exotherm produced from mixing thereactants. Here, specific cooling temperatures are not critical butremain a factor based upon the rate at which the isothiocyanate andpolyether are added together. Accordingly, the reactants should beslowly incorporated to avoid excessive heat build-up from the exothermicreaction. In most cases, the mole ratio for the reactants is about 2moles of the isothiocyanate for each mole of the polyether diamine.

The reaction mixture is then heated, preferably under reflux conditionswhich are at temperatures in the range from 65 to 95 C. and morespecifically at about C. Heating should be continuous for several hoursuntil a homogeneous solution forms which in most instances is waterwhite to straw yellow in color. Solvents initially used to dissolve thereactants are then removed. This can be accomplished by several means,but most conveniently by stripping the mixture at reduced temperaturesand pressures. The temperature is lowered to about 40 to 80 C. and thepressure reduced to 30 to 50 mm. Hg. Ordinarily, a solvent free productcan be secured in about 1- /2 to 3 hours. The final polyoxyalkylenebis-thiourea is H'IN ' a glassy clear to light yellow liquid.

The polyoxyalkylene bis-thiourea extreme pressure lubricants of thepresent invention act by forming protective metal sulfides on thesurface of the workpiece under extreme temperatures and pressures.However, optimal results can best be achieved if these EP agents areused in conjunction with boundary lubricants and specially polar typeboundary lubricants. In the case of the latter, their polar ends, whichmay be the fatty acid or ester portion of the molecule, are absorbedonto the metal surface forming a film, and the non-polar portionsprovide added strength to the film through cohesion.

Preferred boundary lubricants include long chained aliphatic acid soapshaving 8 to 22. carbon atoms in their acid moiety. The cationic moietymay be an alkali metal such as sodium potassium, lithium and ammonium.Others include morpholine, mono, diand tri-ethanolamines,

0 R-ii-o-(X)-o oH,oH,-0

wherein R is a saturated, unsaturated, branched or unbranched chainhaving 7 to 21 carbon atoms, X corresponds to R, however, the formerhave chains of 2 to 16 carbon atoms containing one or more hydroxylgroups and n is 1 to 20. Included in this group are products availableunder the trademark Ethofat by Armour.

Other boundary lubricants for use in accordance with the instantinvention are ethoxylated aliphatic or olefinic alcohols of the formula:

wherein x and y are numbers from 1 to 20. R represents 30 carbon atomsand n is 1 to 20. This group includes ethoxylated cetyl, stearyl oroleyl alcohols having moles of ethylene oxide. Others are thepolyoxyethylene substituted N,N' fatty acid amides available under thetrademark Ethomid by Armour.

Additional agents useful in the instant compositions are ethoxylatedamines of the formula:

wherein x and y are numbers from 1 to 20. R represents salts andaliphatic or olefinic acids of these amines having 8 to 22 carbon atomssuch as oleic and stearic acid. They are sold by Armour under thetrademark Ethomeen.

Specific preferred products are the C/15, C/ and C/ formulations.Further related products include ethoxylated diamines, salts and acidsthereof which can also be employed with the thiourea EP agents. Theyinclude the Ethoduomeen line by Armour.

The present invention also contemplates compositions containing loweralkyl and natural esters of C to C fatty acids such as methyl lardate,ethyl linoleate and methyl tallate.

Generally, EP lubricants of the present invention are used in an amountsufficient to provide anti-weld properties. Though not required in eachinstance, it is advantageous to employ in complete compositions theaforementioned boundary lubricants in an amount suflicient to enhance oractivate the performance of the EP agent. The ratio of EP agent toboundary lubricant is used in the range from about 1:1 to 1:30. Thecombined concentration of EP agent and boundary lubricant informulations should be from 2% to 85%, and when diluted for use, shouldhave a concentration ranging from about 0.03% to 5% and preferably about0.1% to 3.0%.

The extreme pressure agents of this invention can be formulated intonumerous metal working compositions by incorporating the ingredientstogether using conventional, known techniques. The compositions willordinarily be in the form of solutions and emulsions.

Complete metal working compositions are those containing usual basecutting fluids, and preferably for purposes of the instant inventionaqueous base metal-working fluids. Aqueous type fluids are thosecontaining water or are diluted with water prior to use. Aqueous basefluids may be of the soluble oil type which are water emulsifiable, andcontain mineral oils as well as emulsifiers. Emulsifiers commonly usedtherewith may be the mahogany soaps, conventional soaps, rosin acid andtall oil soaps. Any number of nonionic and anionic surfactants such assodium lauryl sulfate, including the phenolate, carboxylate, sulfonatesurfactants and the like can be used with soluble oils.

Compositions of this invention may also contain other adjuvantsfrequently used in metal working fluids such as coupling agents,anti-foam agents, corrosion inhibitors, bactericides, wetting agents,etc. Typical coupling agents are the glycol ethers available under thetrademark Cellosolve which includes their methyl, ethyl and butylhomologues. Other such agents include butyl and amyl alcohol, variouspolyols and mixtures thereof.

Corrosion and rust inhibitors such as borax, sodium nitrite,alkanolamines like diand tri-ethanolamines and condensation products ofdiethanolamine with fatty acids are frequently used. Anti-foam agentsinclude conventional agents such as ester waxes, fatty acid esters ofhigher alcohols such as methyl stearate and tricresyl phosphate. Agentslike O-phenol phenoxide, methyl p-hydroxy benzoate and quaternary aminessuch as Dowicil act to stabilize fluids against fungal or bacterialgrowth. The specific combination of additives used and theirproportional range or ratio in each case will naturally vary dependingon the kind of machining undertaken, the type of metal and operation,whether it is light, medium or heavy duty cutting, grinding, milling,broaching, or whatever.

The polyoxyalkylene bis-thioureas can be used in a broad range ofheavy-duty machining processes. Machining for purposes of this inventionrelates to all types of cutting and grinding on a general basis. Thereare no special limitations in their use, but can be employed wheneverspecial lubrication is indicated. The workpiece is contacted with thefluid by any conventional method. Ordinarily, in the case of small benchand lathe work, manual methods can be used such as brush, roller or handsquirt can applicators. However, for larger floorstand productionmachines, pump pressure circulation, bath or jet spray methods willordinarily be employed.

The following examples illustrate some of the embodiments of thisinvention. It is to be understood that these are for illustrativepurposes only and do not purport to be wholly definitive as toconditions and scope.

A 500 ml. four-neck round bottom flask fitted with a stirrer,thermometer, condenser and addition funnel was charged with 52.1 gramsof a polyether diamine having the following formula:

and dissolved in ml. of isopropyl alcohol. In a second flask, 37 gramsof methyl isothiocyanate was dissolved in 75 ml. of isopropyl alcohol.The dissolved methyl isothiocyanate was slowly added to the dissolvedpolyether over a 45 minute period with stirring. During this time, aslight exotherm occurred. After the addition was completed, the reactionmixture was refluxed at the boiling point of the isopropyl alcohol andallowed to stand overnight. On the following day, the solvent wasremoved by means of a rotating vacuum evaporator. Evaporation wasperformed at 6070 C. and at approximately 30 mm. Hg pressure. The finalproduct had the appearance of a clear oil.

The above product was prepared according to the method of Example I,however, the polyether diamine starting material had a molecular weightof 230 and x was 2.6.

EXAMPLE III Wt. percent EP agent of Example I 4.00 Methyl lardate 7.50Parafiin oil 64.00 Butyl Cellosolve 2.00 Sodium petroleum sulfonate22.00 Methyl p-hydroxybenzoate 0.50

A kettle was charged with the EP agent, butyl Cellosolve, methyllardate, methyl p-hydroxybenzoate and sodium petroleum sulfonate. Theingredients were warmed to 120 to 140 F. and blended until uniform atwhich time the paraffin oil was finally added with stirring.

EXAMPLE IV Wt. percent EP agent of Example I 1.00 Butyl Cellosolve 1.00Ethofat 242/25 6.00 Triethanolamine 10.00 Bactericide (Dowicil 100) 0.50Water 81.50

All ingredients were charged to an open kettle except the water. Thecomposition was stirred until uniform. The water was then added to thekettle.

The mineral oil and petroleum sulfonate salt were added to an open headkettle. The EP agent and methyl lardate were then blended into themineral oil-sodium petroleum sulfonate solution. Finally, the Dowicil100- water-butyl Cellosolve was added as a pre-blend. The blending wascarried out at a temperature in the range of 100 to 140 F.

While the invention has been described in conjunction with specificexamples thereof, this is illustrative only. Accordingly, manyalternatives, modification and variations will be apparent to thoseskilled in the art in light of the foregoing description, and it istherefore intended to embrace all such alternatives, modifications andvariations as to fall within the spirit and broad scope of the appendedclaims.

We claim:

1. A method of machining a metallic workpiece under conditions of hightemperature and pressure, which method comprises contacting theworkpiece with a metal working composition comprising a lubricating basecontaining extreme pressure improving amounts of a compound of theformula:

wherein R and R are selected from the group consisting of hydrogen,alkyl and alkenyl, Y is hydrogen or lower alkyl and x is a number from 1to 10.

2. The method of claim 1 wherein the metal working composition comprisesa compound wherein R and R are methyl, Y is methyl and x is a numberfrom about 3 to 6.

3. The method of claim 1 wherein the metal working composition comprisesa compound wherein R and R are ethyl, Y is methyl and x is a number fromabout 3 to 6.

4. A metal working composition comprising a major amount of an aqueouslubricating base and a minor amount of a compound of the followingformula sufiicient to impart extreme pressure properties to saidcomposition:

wherein R and R are selected from the group consisting of hydrogen alkyland alkenyl in which alkyl and alkenyl have up to 8 carbon atoms, Y ishydrogen or lower alkyl and x is a number from 1 to 10.

5. The composition of claim 4 wherein R and R of the extreme pressureagent are methyl, Y is methyl and x is a number from about 3 to 6.

6. The composition of claim 4 wherein R and R of the extreme pressureagent are ethyl, Y is methyl and x is a number from about 3 to 6.

References Cited UNITED STATES PATENTS 3,704,321 11/1972 Kmet et al.260-552 R 3,579,449 5/1971 Wann et al. 25249.5 3,584,993 1/1971 Myles etal. 25247.5

WARREN H. CANNON, Primary Examiner US. Cl. X.R. 25249.5

